Venus: Problem Child

As the deep basins of Mars fill with the solar system's second planetary ocean, and as the barren slopes of the Elysium massif turn into fruited plains, several generations of planetary engineers will turn their attention from Gaia's first born son. They will begin the monumental task of breathing life into her daughter planet, Venus.

At present, conditions on the surface of Venus are brutal. Surface temperature is around 900 degrees Farenheit (470 degrees Celsius), and atmospheric pressure at the mean surface level is ninety times that on Earth, the same as a diver would experience two hundred feet under water.

To begin to cool the atmosphere, we will need to place a solar shield at the first Cytherian Lagrange point, directly between the planet and the sun. This shield will not shut out the sun completely; our biological activities on Venus will need some insolation. An aperture in the middle of the solar shield will let some light through, about as much as Mars receives on a warm, summer day. We can use the shield to control the bandwidth of the light it allows through, as well as its intensity. The shield will not pass any radiation above the mid-ultraviolet, or below the mid-infrared part of the spectrum. This modulation will allow biological activity to progress without adding any more heat to the already infernal atmosphere than is absolutely necessary.

Venus' unique surface conditions will necessitate having the first settlements at high altitudes. Large, fusion-powered waverider spacecraft will decelerate into the atmosphere until they find a point of neutral buoyancy. There, they will create Venusí first human colony, a collection of inflatable domes. This colony will be floated higher, coming to rest at an altitude where atmospheric pressure equals one atmosphere. There, they will use various bilogical techniques to begin to transform the Cytherean atmosphere. (Cytherea was Aphrodite's island home, and Cytherean used to be the preferred adjective for Venus). Most atmospheric gases need not be imported; they exist in plethoric abundance in Venus' atmosphere. As the colony is built larger, a runway will be constructed for future waverider landings, obviating the need for cargo to be raised to the colony by hydrogen balloons.

Venus is missing one atmospheric constituent that will allow it to be transformed into a living world: hydrogen. Venus' atmosphere already contains almost six times as much nitrogen as Earth's and over four hundred times as much oxygen, including that which exists as part of the atmosphere's main constituent, carbon dioxide. To provide the missing ingredient, we will need one or more short period comets, with a total mass of around 6.5x10 to the 20th power kg. We will disassemble these comets, electrolyze their water, and send the newly produced liquid hydrogen off to Venus, enclosed in an ablating shell. When the hydrogen is exposed to the hot atmosphere, it will vaporize, absorbing heat from the surrounding carbon dioxide, and stealing some of the oxygen to create water vapor. It will then rise to a point where it will give up its heat by condensing, then falling as rain. This rain will not hit the surface at first. For the first few decades, it will cool the upper atmosphere, vaporizing long before it hits the hot, dense lower atmosphere. It will move down slowly, over many years, until it finally hits the surface. The cooling effect provided by this gradually descending rain will be the most important part of the terraforming process.

After the hydrogen bombardment has provided the atmosphere with a noticeable concentration of water vapor, the work of the floating colonies can proceed in earnest. The colonies will breed and release algae into the atmosphere, experimenting with different species, and creating new ones, helping the continuing hydrogen bombardment cleanse the dreaded carbon dioxide from the atmosphere.

After many years, the constant rain will run along the hot surface rocks, cool them, and come to rest in the planet's deep basins. With a quarter of Venus' atmospheric oxygen required to create an Earth normal atmosphere, 3.36x10 to the 20th kg will be left to fill Venus' vast, low plains with an ocean more than one third the volume of the Earth's. With oceans of this size, Ishtar Terra, high in the northern hemisphere, will be the planet's dominant continent, featuring its tallest mountain, Maxwell Montes, which is two kilometers higher than Mount Everest. As the atmosphere gradually thins, the floating colony will gradually descend, eventually coming to rest on Maxwell's summit. Elsewhere on the surface, Aphrodite Terra will be a large equatorial continent, while other elevated regions will form archipelagos of various sized islands. On the other side of the northern hemisphere form Ishtar, Atalanta Planitia will become the center of the Atalantic Ocean.

Venus will always be hotter and wetter than her mother, just as Mars will always be colder and drier. On Mars, the cold dry conditions will result in the formation of high altitude cirrus clouds, which will absorb heat, warming the atmosphere. On Venus, nimbus clouds, which reflect most of the incoming sunlight, will cool the air. These effects, both of which are seen on Earth, are part of a negative feedback loop which will naturally come into existence on a planet with an atmosphere similar to Earth's.

The terraformation of Venus will be a long, time consuming project, but it is an important one. Venus will provide living space for a population almost as large as the Earth's, both on land, and in the thousands of floating colonies that will come to occupy its oceans. The oceans will become home to millions of whales and other marine animals that could not live in our future space colonies, and would have trouble adapting to the low gravity of Mars. Thus Venus will serve as an ark, preserving many terran species in the event of a catastrophe on our mother planet. After hundreds of millions of years of hellish inhospitality, Venus will truly become Earth's sister world.